[PATCH AUTOSEL 6.14 548/642] ipv4: ip_gre: Fix set but not used warning in ipgre_err() if IPv4-only

Sasha Levin
2025-05-05T22:36:23Z

From: Geert Uytterhoeven <geert@linux-m68k.org>

[ Upstream commit 50f37fc2a39c4a8cc4813629b4cf239b71c6097d ]

if CONFIG_NET_IPGRE is enabled, but CONFIG_IPV6 is disabled:

net/ipv4/ip_gre.c: In function ‘ipgre_err’:
net/ipv4/ip_gre.c:144:22: error: variable ‘data_len’ set but not used [-Werror=unused-but-set-variable]
144 | unsigned int data_len = 0;
| ^~~~~~~~

Fix this by moving all data_len processing inside the IPV6-only section
that uses its result.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501121007.2GofXmh5-lkp@intel.com/
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/d09113cfe2bfaca02f3dddf832fb5f48dd20958b.1738704881.git.geert@linux-m68k.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/ip_gre.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index ed1b6b44faf80..c9f11a046c263 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -141,7 +141,6 @@ static int ipgre_err(struct sk_buff *skb, u32 info,
const struct iphdr *iph;
const int type = icmp_hdr(skb)->type;
const int code = icmp_hdr(skb)->code;
- unsigned int data_len = 0;
struct ip_tunnel *t;

if (tpi->proto == htons(ETH_P_TEB))
@@ -182,7 +181,6 @@ static int ipgre_err(struct sk_buff *skb, u32 info,
case ICMP_TIME_EXCEEDED:
if (code != ICMP_EXC_TTL)
return 0;
- data_len = icmp_hdr(skb)->un.reserved[1] * 4; /* RFC 4884 4.1 */
break;

case ICMP_REDIRECT:
@@ -190,10 +188,16 @@ static int ipgre_err(struct sk_buff *skb, u32 info,
}

#if IS_ENABLED(CONFIG_IPV6)
- if (tpi->proto == htons(ETH_P_IPV6) &&
- !ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4 + tpi->hdr_len,
- type, data_len))
- return 0;
+ if (tpi->proto == htons(ETH_P_IPV6)) {
+ unsigned int data_len = 0;
+
+ if (type == ICMP_TIME_EXCEEDED)
+ data_len = icmp_hdr(skb)->un.reserved[1] * 4; /* RFC 4884 4.1 */
+
+ if (!ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4 + tpi->hdr_len,
+ type, data_len))
+ return 0;
+ }
#endif

if (t->parms.iph.daddr == 0 ||
--
2.39.5